// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_ANDROID_LIBRARY_LOADER_LIBRARY_PREFETCHER_H_
#define BASE_ANDROID_LIBRARY_LOADER_LIBRARY_PREFETCHER_H_

#include <jni.h>

#include <stdint.h>
#include <string>

#include "base/debug/proc_maps_linux.h"
#include "base/gtest_prod_util.h"
#include "base/macros.h"

namespace base {
namespace android {

    // Forks and waits for a process prefetching the native library. This is done in
    // a forked process for the following reasons:
    // - Isolating the main process from mistakes in the parsing. If the parsing
    //   returns an incorrect address, only the forked process will crash.
    // - Not inflating the memory used by the main process uselessly, which could
    //   increase its likelihood to be killed.
    // The forked process has background priority and, since it is not declared to
    // the Android runtime, can be killed at any time, which is not an issue here.
    class BASE_EXPORT NativeLibraryPrefetcher {
    public:
        // Finds the ranges matching the native library, forks a low priority
        // process pre-fetching these ranges and wait()s for it.
        // Returns true for success.
        static bool ForkAndPrefetchNativeLibrary();
        // Returns the percentage of the native library code currently resident in
        // memory, or -1 in case of error.
        static int PercentageOfResidentNativeLibraryCode();

    private:
        using AddressRange = std::pair<uintptr_t, uintptr_t>;
        // Returns true if the region matches native code or data.
        static bool IsGoodToPrefetch(const base::debug::MappedMemoryRegion& region);
        // Filters the regions to keep only libchrome ranges if possible.
        static void FilterLibchromeRangesOnlyIfPossible(
            const std::vector<base::debug::MappedMemoryRegion>& regions,
            std::vector<AddressRange>* ranges);
        // Finds the ranges matching the native library in /proc/self/maps.
        // Returns true for success.
        static bool FindRanges(std::vector<AddressRange>* ranges);

        // Returns the percentage of the given address ranges currently resident in
        // memory, or -1 in case of error.
        static int PercentageOfResidentCode(const std::vector<AddressRange>& ranges);

        FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
            TestIsGoodToPrefetchNoRange);
        FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
            TestIsGoodToPrefetchUnreadableRange);
        FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
            TestIsGoodToPrefetchSkipSharedRange);
        FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
            TestIsGoodToPrefetchLibchromeRange);
        FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
            TestIsGoodToPrefetchBaseApkRange);
        FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
            TestFilterLibchromeRangesOnlyIfPossibleNoLibchrome);
        FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
            TestFilterLibchromeRangesOnlyIfPossibleHasLibchrome);
        FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
            TestPercentageOfResidentCode);
        FRIEND_TEST_ALL_PREFIXES(NativeLibraryPrefetcherTest,
            TestPercentageOfResidentCodeTwoRegions);

        DISALLOW_IMPLICIT_CONSTRUCTORS(NativeLibraryPrefetcher);
    };

} // namespace android
} // namespace base

#endif // BASE_ANDROID_LIBRARY_LOADER_LIBRARY_PREFETCHER_H_
